Preheat oven to 375°F (190°C).
Grease a baking dish with butter.
Layer half of the sliced potatoes evenly in the dish.
Sprinkle half of the cheddar and mozzarella over the potatoes.
Repeat layering with remaining potatoes and cheese.
Mix heavy cream, garlic, salt, pepper, and paprika in a bowl.
Pour cream mixture evenly over the layered potatoes.
Drizzle melted butter on top.
Cover with foil and bake for 35 minutes.
Remove foil and bake uncovered for 15 minutes until golden and bubbly.
Garnish with chopped parsley before serving.